1. Field of the Invention
In the broadest sense, the invention pertains to the art of sorting, marking, classifying, or otherwise acting upon moving, solid materials pursuant to the detection or sensing of a particular property or properties found therein (e.g., surface defects, blemishes, cracks). In a more particular sense, the invention has reference to a wholly electronic, sequential event memory incorporating integrated shift registers clocked, timed, or synchronized according to sensed variations in the speed of the conveyed material, or to a known power line or other fixed frequency source, and further incorporating "end signal" suppression circuitry to prevent spurious end signals from detracting from the efficiency of the article detection means.
2. Description of the Prior Art
It is known to detect a particular property of a conveyed object at an inspection location upon a conveyor, and thereafter actuate a mechanism at a control station downstream from the inspection point, to mark, remove, or otherwise act upon the material or object having the sensed property.
However, heretofore equipment designed to discharge this function has been, in many cases, at least partly and in many instances completely mechanical, including discs, tapes, balls, pins, or the like. Efforts have been made to avoid such mechanical couplings, through the use of electrical circuitry. Applicant knows of the following patents representative of the prior art: 3,082,871 Duncan 3,169,424 Branscom et al 3,259,240 Schneider 3,310,169 Forrester 3,352,417 Cutaia 3,543,929 Mattia 3,552,560 Babunovic et al 3,586,168 Osheff et al 3,616,901 Groves 3,656,616 Wallington 3,757,940 Damm
These patents fail to provide a compact assemblage of electrical circuit components, capable of being swiftly installed in association with a conventional conveyor system, and so designed as to accomplish in a single structure, all of the following desirable functions:
First, the use of wholly conventional detection mechanisms, whether photoelectric, electromagnetic, sonic, mechanical or the like;
Second, the optional matching of signal delay time to process velocity so as to "track" variable speed of the conveyor or stop-and-go operation thereof, or alternatively, the clocking of the shift register at selectable rates synchronized to a fixed frequency source such as the power line or a crystal oscillator;
Third, the design of the shift register circuitry such as to optionally incorporate therein a quickly adjustable, selected time delay between the input and output of the shift register utilizing one or more decades of digitally selected delay capability;
Fourth, the adaptability of the device for utilization with any conventional marking, sorting, classifying, or segregating mechanism at the control station;
Fifth, circuitry that possesses maximum reliability, freedom from maintenance, and exceptional, pin-point accuracy; and
Sixth, "end signal" suppression circuitry that avoids the disadvantages of circuits heretofore devised for the same purpose, such as the requirement for two end sensors, the need to place said sensors in close proximity to the article detector, and the difficulty of physically repositioning the end sensors to accommodate system parameter changes.